Displaying progress bar while components load

Question

I'm going to display a JTree that's quite huge (takes time to load; I need to get the info as XML from a server, etc.)
So, I want to display a JProgressBar while it is loading.
My plan was to use a cardlayout, and show the panel with the progress bar until the tree was loaded and then do a .show("tree") on the main panel with the card layout.
However, this does not seem to work. Nothing is displayed before the tree is loaded ...
Any suggestions on best ways to do this?
Here's my class so far:
public class HierarchyJTree extends JPanel {
    private static Logger logger = Logger.getLogger(HierarchyJTree.class);
    private JProgressBar progress;          // keep track on progress
    private TreeMap idmap = new TreeMap(); // to map nodes created up against their id's; needed to create the tree structure when we have a parent id and want the node
    private dataAccess access = dataAccess.getInstance();
    private JTree tree;
    private CardLayout card = new CardLayout();
    private int maxProgress = 20;
     * Construct a new JTree. Collect the category information from the database.
    public HierarchyJTree() {
        this.setLayout(card);
        JPanel progressPanel = new JPanel();
        progress = new JProgressBar(0,maxProgress);
        progressPanel.add(progress);
        this.add(progressPanel, "progress");
        card.show(this,"progress");
    public void startCollectingData() {
        progress.setValue(2);
        ResultSet rs = access.sendXML("<request>\n<runQuery>getCategories</runQuery>\n</request>");
        progress.setValue(10);
        tree = new JTree(new DefaultMutableTreeNode("Categories", true));
        tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
        JPanel treePanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
        treePanel.add(tree);
        this.add(treePanel, "tree");
        addFromResultSetToTree(rs);
        card.show(this, "tree");
     * Constructor that will use incomming ResultSet to create the tree, instead of contacting
     * the server to get a new one
     * @param resultset containing the category info from MOD_category
    public HierarchyJTree(ResultSet resultset) {
        this.setLayout(card);
        tree = new JTree(new DefaultMutableTreeNode("Categories", true));
        BasicConfigurator.configure();
        tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
        addFromResultSetToTree(resultset);
     * This will take a jaxb.ResultSet object containing ID, categoryName and parentID of all the
     * categories in the database, and add them as Nodes in the JTree this class represents.
     * @param r the jaxb.ResultSet object
    private void addFromResultSetToTree(ResultSet r) {
         // code to load the info into the tree here, and inc the progress
            progressValue += incValue;
            progress.setValue((int)Math.round(progressValue));
}

Answer 1

Use SwingWorker, which is not included in Swing library, but you can find it on http://java.sun.com/docs/books/tutorial/uiswing/components/example-swing/SwingWorker.java;
see alse http://java.sun.com/docs/books/tutorial/uiswing/components/progress.html.